Shift mechanism for locking differential



SHIFT MECHANISM FOR LOCKING DIFFRENTIAL Y Filed June l1, 1954 Aug. 20,1957 w. L. PRINGLE 2 Sheets-Sheet 1 Aug. 20, 1957 w. L. PRINGLE2,803,149

Y SHIFT MECHNISM FOR LOCKING DIFFERENTIAL Filed June 11, 1954 2shgts-sneet 2 FLUID PRESSURE SOURCE lof 'A l INVENTOA' AWILLIAM L.PR'nNGLE ATTO SHIFT MECHANISM FOR LOCKING DIFFERENTHAL Mich., assignorto Rock- William L. Pringle, Dearborn,

Coraopoiis, Pa., a corwell Spring and Axle Company, poration ofPennsylvania Application June 11, 1954, Serial No. 436,117

` 4 claims. (C1. 'I4-71ers) This invention relates to vehicle driveaxles, and more particularly to shiftable locking mechanism for the axledifferential and controls therefor.

Motor vehicles equipped with conventional differential axle drives havealways been plagued with traction problems. When vehicles are driven onice or over unusual terrain or through mud, torque transmitted throughsuch conventional drive axle differentials is frequently dissipated byspinning wheels on one side of the drive axle while negligible torque istransmitted to the non-spinning wheels which in many instances may havesufficient traction to sustain reasonably efficient vehicle motion. Whenvariable traction terrain conditions are encountered, a sudden increasein traction by a spinning wheel causes shock loading which may result ina broken axle shaft and/or severe damage to the differential, thevehicle transmission, or other elements in the power train.

Those familiar with this art know that selectively operable vehicledrive axle differential locking arrangements have been proposed andtried to avoid the foregoing difficulties. Much time and effort has beendirected by major automotive concerns and the military services inattempting to develop suitable differential locking mechanisms. Althougha few such locking mechanisms have been made to perform with a measureof success, there have been no simple practical differential lockingmechanisms with sufficient advantages to be generally acceptable asproviding the optimum solution of the problems involved.

All of these prior differential locking mechanisms which have been usedto my knowledge provide for driver control, whereby positive lockingmechanism is activated or inactivated only whenever the driver feelsthat the terrain demands it, and only when the vehicle is stopped andthe power train disconnected. l have discovered that driver judgment islnot particularly satisfactory because in many instances the driver locksout the differential when not necessary and in doing so subjects theaxle shafts to undue strain. For example, under certain conditions theterrain may appear to the driver to require differential lockout whereasactually his momentum and surface conditions, not clearly determinableto him, may combine to provide traction for both wheels. This resultsStates Patent in undue stress on the axle shafts and shortens theirlives. l

Actually I have found that the differential need be locked out only forabout two percent of the operational life of a'heavy duty vehicle, butit will be appreciated that this two percent figure could increasedepending upon the type of service in which the vehicle is used.

According to the present'invention a special arrangement is provided forselectively presetting the differential lockout at any time regardlessof whether the power train is connected or whether the vehicle is in.motion. In practice I provide a fluid motor actuated clutch havingspecial teeth adapted to automatically release under torque overloadconditions, the on-off control for the motor being a manual valveaccessible to the driver. Automatic Mice release of the differentiallockout mechanism when the axle shafts are subjected to predeterminedhigh torques is preferably accomplished by the use of slope sided teethon clutch members which are normally spring biased to released positionand fiuid powered into meshed position.

It is the major object of this invention to provide a reliable driveaxle differential lockout mechanism and associated control thereof whichis effective to lock out the differential substantially only whentraction condi-f.

tions require it.

A further object of the invention is to provide a novel fluid motorpowered clutch mechanism for differential lockout in a vehicle driveaxle.

A further object of the invention is to provide a novel vehicle driveaxle differential lockout mechanism which can be activated orinactivated at any time during normal operation of the vehicle.

A further object of this invention is to provide for automatic releaseof the differential lockout mechanism in the event of predetermined axleshaft torque overload.

The flexibility of operation of this lockout mechanism makes itparticularly adaptable for front drive axles to reduce undesirablesteering effects ordinarily encountered with an unnecessarily lockeddifferential and still retain maximum differential lockout controleffectiveness. It is, therefore, another object of this invention toprovide an improved differential lockout mechanism having minimumadverse steering effects.

A fluid line connector is used in passing the fluid motor supply conduitthrough the axle housing, which effectively seals the housing againstloss of lubricating oil. A further major object of this invention,therefore, is to provide an improved fluid line connector which,although passing through the axle housing, effectively seals the housingagainst loss of lubricant. This connector per se may be of generalapplication.

A further object of the invention is to provide a spring loaded valvecontrol for the differential lockout with a dash mounted operatinghandle.

Another object is to provide this new improved lockout mechanism aseither a conversion kit for existing vehicles or as an assembly forinstallation on new equipment.

A still further object of this invention is to provide a differentiallockout assembly having complete interchangeability of all axleoperating parts whether or not the axle is equipped with a differentiallockout mechanism.

Further objects of the invention will become apparent as the inventionproceeds in connection with the appended claims and the annexed drawingswherein:

Figure 1 is a rear elevation View partly broken away and in section of avehicle drive axle differential equipped with an improved differentiallockout according to a preferred embodiment of this invention;

Figure 2 is a fragmentary top View chiefly in section along line 2 2 inFigure l and in addition shows the external uid power conduit for theclutch operating motor; and

Figure 3 is an end view of the differential lockout clutch looking alongthe axis of the axle toward the wheel with the cutting plane of thesection taken along lines 3-3 in'Figure 2 which shows the mountingbracket, clutch collar and mating parts.

The differential lockout mechanism of this invention is illustrated asbeing used with an otherwise conventional single speed double reductiondrive axle assembly. Input pinion shaft 12 is power driven from theusual vehicle power plant and drive train and extends into housingcarrier 13 where bevel pinion 14 thereon is in constant mesh with abevel pinion 15 on cross shaft 16.

Roller bearing units 17 and 18 support cross shaft 16 andan integralhelical gear 19 which is in constant mesh.

3 with helical gear 21 fastened to the differential cage 22 by boltassemblies 23 which secure the dilerentialcage members 24 and 25together. The differential cage is mounted in a conventional manneronrthe right side of Figure 1 by roller thrust bearingassernbly 26 inone integral arm 27 of carrier 13, being removably secured therein by anannular nut (not shown), and bearing'cap 281 Carrier 13 is provided witha continuous flange 31" through which extend studs 32 to removablymountthe carrier upon a coacting liange 33 of axle housing 34, flange 33surrounding the usual opening in the axle housing so that when the studnuts at 32 are tightened the dilerential is located within the centersection of axle housing 34.- Al

circumferential series of these studs 32 are arranged about theilange33.

Referring now to Figure 2 the other usualintegral carrier arm 35 isillustrated somewhat out ofy position. It has a bore 36 in which ismounted the outer race of a roller thrust bearing unit 37 whose innerrace is press fitted upon the outer end portion of cage halfA 25 andabuts a radial shoulder 3S on cage half 25. An annular nut 39 threadedin the carrier arm 35 and coacting bearing cap 41 engages the outer raceof the bearing and provides the bearing adjustment.

A conventional axle shaft 43 extends through cage half 24 into splinedengagement with one side gear 44 of the differential. The other sidegear 44 is mounted conventionally within the cage and a spider 45carries the usual pinion gears 46 meshed with both side gears.

The other axle shaft 47 is different from axle shaft 43 by reason of alonger splined section 48 that is conventionally mounted at its innerend within the splined hub of left side gear 44 of Figure l. The purposeof this long splined section 48 will later be described.

Cage half 25 differs from cage half 24 essentially in that the formerterminates beyond bearing 37 in an axially directed row of clutch teeth51 which have at end faces 52 perpendicular to the axis of shaft 47 andsloping side faces 53 for a purpose to appear.

A differential lockout clutch collar 50 is non-rotatably but axiallyslidably mounted on the splined axle shaft section 48 by internalsplines 54 and its inner end is provided with flat end sloping sideteeth 55 cut to mate with the cage teeth 51. The collar 50 is providedwith a radial shoulder 56 abutted by an annular thrust piston 57 for ashift to clutching engagement of teeth 55 and 51. At the end oppositeteeth 55 a collar snap ring 58 fits in a groove of collar 50 andreceives axial thrust from piston 57 through thrust Washer 59 todisengage teeth 55 from teeth 51 when piston 57 is not actuated by fluidpressure as will appear.

Referring also to Figures 2 and 3 piston 57 is reciprocable within asupport cylinder 61 integrally formed with two mounting arms 62 whichextend laterally from each side of the cylinder and upwardly andinwardly to terminate in bosses 63 having bores 64 through which passtwo of the studs 32 which are for this reason longer than the otherstuds. When nuts 65 are tightened the cylinder 61 lis fixed to the axlehousing with cylindrical bores 66 and 67 coaxial with shaft 47.Reenforcing webs 68 are provided for arms 62.

Annular spring backing plate 71 freely surrounds the inner end of clutchcollar 50 and is retained against outward axial shift in bore 66 by snapring 72 fitting in groove 73. Piate 71 is fixed against rotation by twotongues 74 which radially project into slots 75 in cylinder 61 as shownin Figure 3. Figure 2 illustrates in section one such tongue 74 in aslot rotated 90 out of position.

Recesses 76 provided in piston 57 receive and guide a series of coisprings 77 compressed between the piston 57 andplate 71, to resilientlybias piston 57 and clutch collar 50 toward the clutch disengagedposition of Figure 2. Guide pins 70 are fixed in piston 57, and freelyslidably pass through apertures 79 in spring backing plate 71 to preventrotation of the piston 57 within the cylinder.

Annular piston 57 which is thereby non-rotatably mounted in cylinder 61has an inner cylindrical bore 81 in surrounding spaced relationship tothe cylindrical surface 82 of collar 50 which rotates with axle shaft47. The enlarged portion 83 of piston 57 has a sliding fit in cylinderbore 66, and the reduced portion 84 of the piston 57 has a sliding t inbore 67. Seal rings 85 and 86 which are preferably of the uniform crosssection rubber O-ring type are provided in suitable surface grooves inthe piston portions to coact with bores 66 and 67 to prevent the escapeof uid from, and the ingress of oil into, an annular chamber 87 which isrecessed into the corner provided by the intersection of bore 66 withradial flat wall 8S which serves as a stop to limit outward displacementof piston 57.

Annular cylinder chamber 87 communicates with a threaded bore 89 in thewall of cylinder 61. Adjacently the axle housing is formed with athreaded bore 91 in which is mounted an annular plug 92 having ahexagonal head 93. The hexagonal head 93 at the outer end of plug 92 isprovided with a spherical sealing seat 94 for a resilient seal 95 whichmay bernoulded rubber. An inner connector 96 has a hexagonal head 97 anda tubular shank 98 which projects with ample clearance through opening99 0f plug 92 and is threaded at end 101 to fit into bore 89. Threadedopening 102 of connector 96 receives a conventional terminal fittingassembly 103 on the end of a conduit 104.

Connector 96 is tightened with threaded end 101 in the threaded bore 89of the cylinder 61, causing washer 90 to compress resilient seal 95 intospherical seat 94. The ample clearance provided between tubularconnector shank 93 and plug bore 99 and spherical seat 94 is to allowfor any misalignment. Rubber seal 95 prevents loss of oil from the axlehousing and cushions any vibration or relative motion between cylinder61 and the axle housing transmitted to inner connector 96. In some axleembodiments plug 92 may be eliminated, and an opening comparable toopening 99 and a spherical seat similar to seat 94 may both be directlyprovided in housing 34.

The iiuid line 104 is connected to any available source of air pressuresuch as the conventional air brake supply tank 105 through a valve 106.Valve 106 is conveniently mounted at a point readily accessible to thedriver so that when manual handle 107 is turned counterclockwise inFigure 2, valve passage 100 in the rotatable valve element will alignwith conduit 104 and air pressure will be supplied to the differentiallockout unit cylinder to force clutch teeth 55 into mesh with teeth 51.Handle107 is preferably biased by a spring 108 so that when it isreleased it automatically returns to off position and irnmediatelypermits separation of the clutch teeth in the dilerential lock-outmechanism. By this control arrangement the differential lock-out isintroduced only when the driver desires it.

A pivoted latch 109 is provided to hold handle 107 in valve openposition `so that the differential lock-out will' be activated so longas handle 107 is held in this position. To eliminate drivinginadvertently with the differential llocloout activated, a buzzer 111 orsignal lamp 112 may be energizedw through latch controlled switch 113 asa reminder that the differential lock-out controls are in the onposition. To unlatch handle 107 the operator manually lifts latch 109thereby allowing handle 107 to spring back to off position. It isdesirable that the lockout be deactivated when not needed even though itmay be' lleft in the activated locked state when operating on thehighway without fear of trouble.

Referring'to Figure 2, the illustrated end of cage half 25 is composedof a conventional differential cage half cut off at region to interfitwith and be Welded as at 121 to a special end portion 122 bearing theclutch teeth 55. This represents a standard cage half modified forpurposes of the invention. However, it will be apprel f ciated thatequivalently the end portion 122 could be integral with the remainder ofcage half 25.

In normal operation with the controls and parts in the off position ofFigure 2 the axle shafts are differentially driven as in the usual axle.When the need for differential lock-out arises, or appears to arise, theoperator moves handle 107 to the on position held by latch 109 to openvalve 106 permitting air pressure to be applied through conduit 104 tocylinder chamber 87. This causes piston 57 to engage shoulder 56 onclutch collar 50 thus causing clutch collar 50 to slide to the right inFigure 2 and force clutch teeth 55 into engaged ment with mating teeth51. Teeth 51 are rigidly connected to the rotating casing of thedifferential. Since clutch collar 50 is splined to axle shaft 47, theengagement of teeth 55 with teeth 51 locks differential side gear 44with respect to the differential cage thus eliminating any differentialaction, and the rotating collar 50 is axially restrained relative topiston 57 by washer 59 and shoulder 56.

Annular spring backing plate 71 is xed to cylinder 61. Therefore whenthe clutch teeth are engaged springs 77 are compressed. When the valve106 is returned to the Figure 2 position the force stored in springs 77disengages the clutch teeth.

An important feature of the invention is that the/ differential lockoutclutch will be disengaged whenever the axle shaft torque loading exceedsa predetermined value. The automatic disengaging feature is due to theuse of the sloping side surface clutch teeth. A component of the axledriving torque is caused by these sloping surfaces to be transformed toa force directed parallel to the axle axis tending to separate theclutch parts and 50. If side faces 53 were perpendicular to surface 52,no force tending to separate the clutch parts would be present. Theforce tending to hold the engaged clutch parts together is the force duetothe product of the piston area and the line pressure less the forcedue to the compressed springs.

When the clutch teeth are meshed and torque is being transmitted throughthe axle shaft to the associated wheel, the clutch parts are heldtogether due to the force of the air motor and friction due to thattorque. Should the wheel encounter a dry spot which would suddenlyincrease its traction to a point Where the drive torque exceeded apredetermined value, the developed axial force component due to theslanting face clutch teeth would overcome that engaging force and thefriction and force the clutch parts apart to disengage them. Should thatcondition suddenly disappear the clutch will be automatically engaged atonce.

.In one specific embodiment given by way of example usmg gear teethhaving a 91/2" angle of slope for side faces 53 and approximately 400pounds exerted by piston 57, the lockout mechanism automaticallydisengaged when the drive axle shafts were subjected to a torquedifference less than the torsional breaking point of any of the driveaxle or differential parts.

This type of lockout mechanism is especially useful for front wheeldrives in vehicles because the fluid pressure, the area of the pistonand slope of the teeth can all be chosen so that the clutch willautomatically disengage when a predetermined axle shaft torquedifference, for example, 75% of the torque that is required to slip thetires of one axle shaft under normal static loads when the tires of theother axle shaft are freely slipping is present. This greatly reducesthe undesirable steering effects normally present when the frontdifferential is locked out and still gives the advantages of alocked-out differential insofar as traction is concerned. Even thoughkshock loading may result when the teeth repeatedly come together duringautomatic disengagement caused by a torque overload on the axle, the useof sloped teeth 6 prevents this loading from exceeding a predeterminedsafe value.

There is provided by my invention a new improved fluid shift clutchingdifferential lockout contained within an axle housing and selectivelyoperable at any time during the operation of the vehicle. The selectivecontrol by the vehicle driver of the lockout mechanism permits thedifferential to be locked out only when necessary and therefore preventsunnecessary axle loading and consequently increases axle shaft fatiguelife and differential wear life. This invention further provides adifferential lockout mechanism which may be supplied as a conversion kitconsisting of a special toothed end differential cage half like 25 andthe piston and clutch half assembly mounted on cylinder 61 and arms 62,together with the necessary conduit and conduit connections shown inFigure 2, or installed as original equipment in drive axles, and, whenused with front drive axles greatly reduces the undesirable steeringeffects. It further provides a lockout clutch release automaticallyoperable at a predetermined safe percentage of axle shaft torquecapacity and the necessary components comprise a light compact assemblywhich can be incorporated in a conventional axle housing.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is, therefore, to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and`range ofequivalency of the claims are, therefore intended to be embracedtherein.

What lis, claimed and desired to be secured by United States LettersAPatent yis:

- l. In combination with a vehicle drive axle assembly including ahousing provided with a central differential receiving portion, adifferential carrier having spaced arms providing bearing yseats andextending Within said axle housing and a peripheral attachment flangesecured to an abutting face Vof said axle housing, a differentialmechanism journalled on said carrier within said axle hou-singdifferential receiving portion by spaced bearings mounted in the bearingseats of said arms, a pair of oppositely extending axle shafts mountedrespectively in the oppositely extending portions of said `axle housingprojecting from the differential receiving portion and drive connectedat their adjacent ends to the side gears `of `said differentialmechanism, a first toothed clutch component fixed to one end of the cageof said differential mechanism exteriorly of one of the bearingsjournalling said differential mech- `anism in surrounding relation toone of said axle shafts, an assembly adapted to coact with said clutchcomponent t-o provide a torque overload release lockout for saiddifferential mechanism and comprising a mounting bracket having acentral portion of generally annular configuration surrounding said oneaxle shaft and oppositely extending arms secured to said axle housing atthe mounts for said differential carrier, a second toothed clutchcomponent complementary to said first clutch component and splined tosaid one axle shaft Within the annular portion of said bracket, andcapable of axial movement along said axle shaft, an annular fluid motorsurrounding the second said clutch component within said bracket annularportion and operatively connected thereto t-o shift said second clutchcomponent to couple said differential cage and said one axle shaft forconcomitant rotation, said complementary clutch components having theaxially extending teeth of trapezoidal cross section in said axialdirection to provide opposed inclined faces of such relative inclinationthat an increase in torque transmitted between said clutch componentsproduces concomitant increase in axial separating force between saidclutch components and means selectively actuated to connect said fluidmotor to a source of fluid pressure whereby upon development of apredetermined torque between said differential cage-and saidy one axleshaft, said second clutch component will be shifted to its disengagedposition in opposition to the fluid pressure bias exerted thereon bysaid fluid motor.

2. The combination defined in claim 1 wherein said means -forselectively energizing said uid motor includes a source of fluidpressure and the fluid pressure transmitting conduit extending from saidsource through said axle housing to said fluid motor.

3. fn combination with a vehicle drive axle assembly including a housingprovided with a central diiferential receiving portion, a differentialcarrier having spaced arms extending within said axle housing, meanssecuring said carrier to said axle housing, a differential cagejournalled on said carrier Within said axle housing differentialreceiving portion by spaced bearings mounted in said arms, differentialmechanism within said cage including spaced side gears, a pair ofoppositely extending axle shafts mounted respectively in the `oppositelyextending portions of said axle housing projecting from the differentialreceiving portion and -drive connected at their adjacentv ends to saidside gears, a first toothed clutch component fixed to one end of saiddifferential cage exteriorly of' one of said bearings in surroundingrelation to one of said axle shafts, means adapted to coact with saidrst clutch component to provide a torque overload release lockout forsaid differential mechanism and comprising a mounting bracketsurrounding said one axle shaft and having oppositely extending armssecured to said axle housing, a second toothed clutch componentcomplementary to said rst clutch component and slidably splined to saidone laxle shaft so as to be capable of axial movement along said axleshaft, an annular fluid pressure responsive motor carried by saidbracket -coaxial with the second said clutch component operativelyconnected to selectively shift said second clutch ycomponent to engagesaid first clutch component to couple said differential cage `and saidone axle shaft for concomitant rotation, said complementary clutchcomponents having the axially extending teeth of substantiallytrapezoidal cross section in said axial direction to provide opposedinclined faces of such relative 4inclination that an increase in torquetransmitted between the engaged clutch components produces concomitantincrease'in axial separating force between said clutch components andupon development of a predetermined torque between said differentialcage and said one axle shaft said second clutch component will beshifted to its disengaged position, and means selectively actuated toconnect said motor to a source ofuid pressure outside the axle houslng.

4. In a'vehicle drive axle assembly, a housing, a differentialcagemounted within said housing for rotation about 4a11,axis,.an axleshaft projecting from one side of said cage, a` yclutch collarnon-rotatably and slidably mounted on said k.shaft adjacent said cage,coacting clutch teeth on the collarand cage, anda fluid pressureresponsive motor for. actuating said. clutch collar comprising a supportmounted within said housing having a cylinder concentric with saidshaft, a reciprocable piston in said cylinder, means operably connectingsaid piston and collar so that reciprocation of said pistoncorrespondingly slides said collar, said means providing relativerotation between the collar and piston, means for introducing fluidunder pressure through thel axle housing into said cylinder, andresilient piston return means normally urging said piston andmcollartodisengage said clutch teeth, said resilient means being energized whensaid piston is advanced under fluid pressure to engage said clutchteeth.

References Cited in the file of this patent UNITED STATES PATENTS1,355,297 Woodward Oct. 12, 1920 1,464,795 Woodward Aug. 14, 19231,488,581 Woodward Apr. l, 1924 1,494,457 Woodward May 20, 19241,515,916 Woodward Nov. 18, 1924 2,057,744 Sanford Oct. 20, 19362,137,249 Sanford NOV. 22, 1938 2,580,381 Banker Jan. 1, 1952 2,620,055Fasulo Dec. 2, 1952 FOREIGN PATENTS 56,771 France July 30, 1952

